Work

The effect of embryo vitrification duration on frozen-thawed transfer outcomes: the key moderating role of age—a retrospective cohort study of 13,054 cycles

Year: 2026

Type: article

Abstract: Purpose To investigate how embryo vitrification duration affects frozen-thawed transfer outcomes, focusing on the interaction between age (at transfer and at freezing) and storage time. Methods This retrospective cohort study included 13,054 first vitrified embryo transfers (2015–2025). Cycles were divided by cryopreservation duration: ≤0.5, 0.5-2, 2–5, and > 5 years. Primary outcomes were clinical pregnancy, implantation, and live birth rates; secondary outcomes included biochemical pregnancy, miscarriage, ectopic, and multiple pregnancy. Multivariate logistic regression adjusted for confounders, followed by age-stratified analyses and interaction tests. Subgroup analyses used age at transplantation (ROC cutoff 36 years) and at freezing (cutoff 34.5 years). Results Compared to ≤ 0.5 years, the > 5 years group showed lower clinical pregnancy (aOR = 0.757, P = 0.036), implantation (aOR = 0.604, P = 0.001), and live birth rates (aOR = 0.881, P = 0.003). For 2–5 years, only live birth rate decreased (aOR = 0.875, P = 0.049). Age significantly interacted with freezing duration (P = 0.001). Women aged ≤ 34.5 years at freezing also exhibited a dose-response decline in live birth rates with longer storage. Conclusions Long-term cryopreservation (>5 years) has an adverse effect on the outcomes of frozen-thawed embryo transfer, but this effect is observed only in younger women. In older women, the deterioration of the uterine environment may mask the additional risks associated with prolonged cryopreservation. Clinicians should make individualized decisions regarding the use of long-term cryopreserved embryos by considering both the patient’s age at the time of transfer and the age of the embryos at the time of cryopreservation.

Source: Journal of Assisted Reproduction and Genetics

DOI: 10.1007/s10815-026-03981-4

Authors: Yongxuan Ji, Ying Zhang, Huanze Cao, Ning Zhang

Institutions: Shandong University of Traditional Chinese Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine

Language: English

Topic: Reproductive Biology and Fertility

Subfield: Reproductive Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green

Funder: Shandong University